1 files changed, 12 insertions, 3 deletions

diff --git a/kernel/pid.c b/kernel/pid.c
index 36aa02ff17d6..de9af600006f 100644
--- a/kernel/pid.c
+++ b/kernel/pid.c
@@ -270,7 +270,6 @@ void free_pid(struct pid *pid)
                         wake_up_process(ns->child_reaper);
                         break;
                 case 0:
-                        ns->nr_hashed = -1;
                         schedule_work(&ns->proc_work);
                         break;
                 }
@@ -319,7 +318,7 @@ struct pid *alloc_pid(struct pid_namespace *ns)
 
         upid = pid->numbers + ns->level;
         spin_lock_irq(&pidmap_lock);
-        if (ns->nr_hashed < 0)
+        if (!(ns->nr_hashed & PIDNS_HASH_ADDING))
                 goto out_unlock;
         for ( ; upid >= pid->numbers; --upid) {
                 hlist_add_head_rcu(&upid->pid_chain,
@@ -342,6 +341,13 @@ out_free:
         goto out;
 }
 
+void disable_pid_allocation(struct pid_namespace *ns)
+{
+        spin_lock_irq(&pidmap_lock);
+        ns->nr_hashed &= ~PIDNS_HASH_ADDING;
+        spin_unlock_irq(&pidmap_lock);
+}
+
 struct pid *find_pid_ns(int nr, struct pid_namespace *ns)
 {
         struct hlist_node *elem;
@@ -573,6 +579,9 @@ void __init pidhash_init(void)
 
 void __init pidmap_init(void)
 {
+        /* Veryify no one has done anything silly */
+        BUILD_BUG_ON(PID_MAX_LIMIT >= PIDNS_HASH_ADDING);
+
         /* bump default and minimum pid_max based on number of cpus */
         pid_max = min(pid_max_max, max_t(int, pid_max,
                                 PIDS_PER_CPU_DEFAULT * num_possible_cpus()));
@@ -584,7 +593,7 @@ void __init pidmap_init(void)
         /* Reserve PID 0. We never call free_pidmap(0) */
         set_bit(0, init_pid_ns.pidmap[0].page);
         atomic_dec(&init_pid_ns.pidmap[0].nr_free);
-        init_pid_ns.nr_hashed = 1;
+        init_pid_ns.nr_hashed = PIDNS_HASH_ADDING;
 
         init_pid_ns.pid_cachep = KMEM_CACHE(pid,
                         SLAB_HWCACHE_ALIGN | SLAB_PANIC);